Hydraulic fluid device and method of assembly thereof

ABSTRACT

A hydraulic fluid device includes a cylinder block, a plurality of pistons with inner ends disposed for reciprocation within cylinders in the cylinder block, and an inclined cam plate having a bearing surface facing one end of the cylinder block. The outer ends of the pistons have bearing means in the form of a slipper which slidably follows the bearing surface on the cam plate. The cylinder block is mounted for rotation relative to the cam plate. A fluid inlet and outlet means communicates successively with ports in the cylinder block upon rotation of the cylinder block relative to the cam plate. The cylinder block has a hub portion projecting therefrom and a spherical collar is pressfit on the hub portion. A slipper retainer plate is supported on the spherical surface of the collar and is engageable with the slipper, and a spring means biases the cylinder block and collar in a direction to create a predetermined clearance which during running provides a clearance between the retainer plate and the slipper. The hydraulic fluid device is assembled by a process in which the cylinder block is pressfit part way into the spherical collar and the assemblage thereof is placed in the housing of the hydraulic fluid device. A fixture or ram member is then engaged in a cooperative association with the cylinder block and moved inwardly to move the cylinder block farther into pressfitting relationship with the spherical collar. The fixture is then removed and a cover is bolted onto the housing. The spring means then biases the cylinder block and collar in a direction toward the cover for the housing. These steps result in the predetermined clearance referred to above being established.

llnited States Patent [191 llenkovic Ian. D, 11974 HYDRAULIC FLUID DEVICE AND METHOD OF ASSEMBLY THEREOF [75] Inventor: Roger J. Benkovic, Marshall, Mich.

[73] Assignee: Eaton Corporation, Cleveland, Ohio [22] Filed: Apr. 24, 1972 [21] Appl. No.: 246,829

Primary Examiner-Martin P. Schwadron Assistant ExaminerAbe Hershkovitz Att0rneyJoseph R. Teagno et a1.

[5 7] ABSTRACT A hydraulic fluid device includes a cylinder block, a plurality of pistons with inner ends disposed for reciprocation within cylinders in the cylinder block, and an inclined cam plate having a bearing surface facing one end of the cylinder block. The outer ends of the pistons have bearing means in the form of a slipper which slidably follows the bearing surface on the cam plate. The cylinder block is mounted for rotation relative to the cam plate. A fluid inlet and outlet means communicates successively with ports in the cylinder block upon rotation of the cylinder block relative to the cam plate. The cylinder block has a hub portion projecting therefrom and a spherical collar is pressfit on the hub portion. A slipper retainer plate is supported on the spherical surface of the collar and is engageable with the slipper, and a spring means biases the cylinder block and collar in a direction to create a predetermined clearance which during running provides a clearance between the retainer plate and the slipper.

The hydraulic fluid device is assembled by a process in which the cylinder block is pressfit part way into the spherical collar and the assemblage thereof is placed in the housing of the hydraulic fluid device. A fixture or ram member is then engaged in a cooperative association with the cylinder block and moved inwardly to move the cylinder block farther into pressfitting relationship with the spherical collar. The fixture is then removed and a cover is bolted onto the housing. The spring means then biases the cylinder block and collar in a direction toward the cover for the housing. These steps result in the predetermined clearance referred to above being established.

8 Claims, 4 Drawing Figures PATENTEUJAN a 1974 SHHY 2 BF 3 r m 8% u sum 3 or 3 PATENTEUJAH s 1974 Q 4 NM m \M N m \m I muw m6 Q B mm mm NM \m mN kw HYDRAULIC FLUID DEVICE AND METHOD OF ASSEMBLY THEREOF The present invention relates to a hydraulic fluid device and a method of assembly thereof, and particularly relates to a hydraulic fluid device of the axial-piston type and to a method of assembling the same.

Hydraulic fluid devices in the form of pumps and motors are well known and the art of axial piston pumps andd motors is an extremely well-developed art. Axial piston pumps and motors include a cylinder block which carries a plurality of pistons. Each piston is connected to a slipper which slides on a bearing surface. As the pistons are communicated with high and low pressure, relative rotation occurs between each slipper and the bearing surface. Much work has been done relating to structures for establishing and limiting the maximum clearance between the slipper retainer plate and the slipper. In addition, much work has been done in the area of assembly techniques for such hydrostatic transmissions to achieve the above-mentioned clearance. U.S. Pat. No. 3,274,897 and U.S. Pat. No. 3,292,553 are directed to hydraulic fluid devices of the axialpiston type in which such clearances and assembly techniques providing therefor are disclosed.

The present invention is directed to such hydraulic fluid devices in which a predetermined clearance is established between the slipper retainer and slippers. In accordance with the present invention the slipper retainer abuts a portion of the slippers and is supported centrally on a spherical collar which is pressfit on a projection of the cylinder block which carries the pistons. The cylinder block is biased and the spring which biases the cylinder block also biases the spherical collar in a direction away from the bearing surface on which the slippers run. Accordingly, the construction is such that a predetermined clearance is provided for between the slippers and the slipper retainer during the assembly of the unit.

The hydraulic fluid device embodying the present invention is assembled by a technique in which the cylinder block is partially pressflt into the spherical collar and the. spherical collar and cylinder block are assembled with the pistons, slipper and the slipper retainer plate. This assemblage is then placed within the housing of the device in which the cam plate having the bearing surface is positioned. The slipper is located in engagement with the bearing surface andd the slipper retainer plate engages the slipper. Due to the partial pressfitting of the cylinder block with the spherical collar, that assemblage has a greater axial length than it has after final assemblage. A valve plate is placed on the end of the cylinder block and a fixture is then engaged with the outer surface of the valve plate and moved axially to further press the cylinder block into the spherical collar. The pressing 'of the cylinder block into the spherical collar causes a compression of a spring which acts between the shaft of the fluid device and the cylinder block. The collar transmits the force applied thereto by the fixture to the slipper retainer,

slipper and cam plate, and accordingly is restrained from movement. When the fixture is removed and a housing end plate is secured in position, the aforementioned spring biases the cylinder block as well as the spherical collar axially relative to the cam plate and slipper. The movement of the cylinder block and the spherical collar by the spring creates a clearance'which during operation establishes the clearance between the retainer plate and the slipper.

Further features of the present invention will be apparent to those skilled in the art to which it relates from the following detailed description of a preferred embodiment thereof made with reference to the accompanying drawings in which:

FIG. I illustrates a hydraulic fluid device embodying the present invention and which is in its final assembled form; and

FIGS. 2, 3 and 4- illustrate, somewhat schematically, the various sequential steps in the assembly of the hydraulic fluid device shown in FIG. I.

The present invention relates to an improved hydraulic fluid device of the axial piston type. The present invention may be applied to a pump or motor unit of either a fixed or variable displacement. As shown in the drawings, the invention is applied to a variable displacement hydraulic motor, but it should be understood that the invention is equally applicable to a fixed displacement motor or a fixed or variable displacement pump.

As shown in the drawings, the variable displacement axial piston fluid motor is generally designated I0. The fluid motor III, as is well known, has an output shaft I I which may be suitably connected for driving a load. The shaft Ill is supported at its one end (left end in the drawing) by a bearing I2 which is received in a housing part I3. The shaft II extends centrally through the housing and is supported by a housing cover portion IS. The housing also has a generally cylindrical-shaped housing portion 16 which is suitably secured to the housing portion I3 at one end and to which the cover portion I5 is fastened by suitable screws I6a extending 7 a cylinder block 2@ which contains a plurality of pistonreceiving passages or bores 2I therein. A piston 22 is received in each of the bores 21 and is slidable therein.

A suitable sleeve member 23 is located in the bores 2I and receives the piston 22 therein.

The outer end of each piston 22 is connected with a slipper member 23 and specifically a spherical outer end 2d of each piston 22 is connected in a spherical recess 25 in the slipper member 23. As noted above, the slipper 23 is connected with each of the piston members 22, but only one of which is shown in the drawings. Each slipper member 23 has a bearing surface 30 which is engageable with the bearing surface 3a of a thrust plate or cam plate M. The thrust plate 3I is inclined and carried by a swashplate member 32. The swashplate member 32 is movable so as to vary the inclination of the cam plate or thrust plate 3I, as is well known. In the position shown in FIG. I, the swashplate member 32 is in engagement with the housing member I3.

Each of the cylinder bores 21 has a port 40 which communicates with ports in a valve plate 42. The right end surface II of the cylinder block 20 runs in engagement with the inner surface of the valve plate 42. The valve plate 42 is provided, as is well known, with ports for communicating high fluid pressure to the cylinder bores 21 and for communicating the cylinder bores 21 to low pressure. The valve plate 42 is suitably secured to the end housing plate by a suitable key 45 in order to prevent rotation of the valve plate. Any suitable arrangement may be used for delivering and exhausting fluid from the cylinder bores 21. As is well known, in response to the fluid flow into and out of the cylinder 20, the piston members 22 are reciprocated in the bore 21 and as a result, the cylinder block is rotated thereby.

The rotation of the cylinder block 20 is transmitted to the output shaft 11 through a spline connection 50 which is provided between the cylinder block and the shaft 11. The spline connection 50 comprises splines on a projecting hub portion 51 of the cylinder block 20 and which engage with a spline portion of the output shaft 11.

The projecting portion or hub 51 of the cylinder block 20 is pressfit into a bore in a spherical collar member 52. The pressfit connection is at 53 in FIG. 1. The collar member 52 accordingly rotates with the cylinder block 20. The outer surface 55 of the collar member 52 is a spherical surface and riding on that spherical surface 55 is a slipper retainer plate member 57. The slipper retainer plate member 57 has a conical surface 58 (which may also be spherical) which rides in engagement with the spherical surface 55 of the collar member 52. The retainer member 57 upon rotation of the cylinder block 20 and reciprocation of the piston 22 nutates about an axis passing through the center of the spherical collar 52 and limits the movement of the slipper member 23 away from the thrust member 31.

When the motor unit 10 is assembled, a clearance space is provided between the retainer plate 57 and the flanges 23a of the slipper 23. The clearance space is provided due to the assembly technique, to be described hereinbelow, and by the action of a spring 62 which acts to bias the cylinder block 20 and the spherical collar 52 toward the right, as in FIG. 1, against the valve plate 42 which in turn is urged against the cover or housing member 15.

The spring member 62 acts at one end against a collar 63 which in turn engages a shoulder 64 on the shaft 11. The other end of the spring 62 acts against a collar 65 which in turn acts against a snap-ring 66 which is received in a groove 67 in the cylinder block 20. Accordingly, it should be apparent that the spring 62 biases the cylinder block 20 toward the right, as viewed in FIG. 1. Also, it should be apparent that since the collar 52 is pressfit, at the pressfit connection 53, to the hub portion 51 of the cylinder block 20, the collar 52 is likewise biased to the right by the spring 62.

During operation of the motor 10, fluid pressure is communicated to the area between the slipper bearing surface and bearing surface 3 0a on the thrust plate 31 by suitable fluid passages in the piston and slipper 23. An orifice is provided in the piston and a pressure drop is provided thereby across the slipper 23 tending to urge the slipper 23 into engagement wtih the cam surface a of the thrust plate 31. As the piston members 22 move or reciprocate, the slipper member 23 engages and moves the retainer plate 57 therewith. However, due to the fact that a predetermined maximum clearance 60 is provided between the slipper and retainer plate, the slipper 23 cannot move in excess of that amount relative to the retainer plate 57 and vice versa due to some abnormal operating conditions.

The motor unit 10 is assembled in a unique manner and the various steps in the assembly technique are illustrated in FIGS. 2-4. Initially, the housing is assembled with the swashplate 32 and thrust plate 31 in position therein. The cylinder block 20 is then pressfit onto the collar 52. However, the cylinder block 20 is not pressed into the bore in the collar 52 to the final operative interrelationship thereof. The difference between where the cylinder block is actually positioned at this stage in the assembly and where it is positioned in the final assembly is designated in the drawings as dimension A (FIG. 2).

After the cylinder block 20 and the collar 52 are partially pressfit together to the relationship shown in FIG. 2, the pistons 22, slipper 23 and retainer plate 57 are assembled together with the cylinder block 20 and collar 52. This assemblage of the rotary group, namely, the pistons 22, slipper 23, retainer plate 57, cylinder block 20 and collar 52 is then inserted in a telescoping manner over the end of the shaft 1 1 so that the slipper bearing surface 31 engages the bearing surface 30a of the thrust plate 31. The rotary group is inserted into the housing through the axial end thereof which, as yet, does not have end cover 15 secured in position. The collar 63 is then positioned on the shaft 11 and the spring 62, collar and snap-ring 66 are likewise positioned, as shown. It should be apparent, of course, that in this positioning the spring 62 has a greater length by a dimension B (FIG 2) than what it has in the final assemblage of the unit.

Once this assemblage has taken place, as shown in FIG. 2, the valve plate 42 is positioned in engagement with the surface 41 of the cylinder block 20 and a suitable gasket 69 is positioned on the end of the housing member 16, as shown in FIG. 3.

Also as shown in FIG. 3, a fixture designated 70 is then positioned and engaged with the outer surface of the valve plate 42. The fixture 70 has a projecting ram portion 71 which is adapted to engage and move the valve plate 42 and cylinder block 20 axially of the housing. In order to move the cylinder block 20, suitable provision is made for the ram portion 71 to clear the shaft 11 and not interfere therewith. There is a recess around the periphery of the fixture 70 defining a shoulder surface portion 75 of the fixture 70 which is spaced from the gasket 69 by a distance designated C.

The fixture 70 is then moved axially inwardly of the unit and applies a pressure force against the valve plate 42 which is transmitted to the cylinder block 20, and the projecting hub portion 51 of the cylinder block 20 is moved thereby farther into the bore of the spherical collar 52. The spherical collar 52 at this point cannot move under this action due to the fact that the collar 52 is in engagement with the retainer plate 57 which in turn is in engagement with the slipper flanges 23a and the slipper 23 is in engagement with the thrust plate 31 which in turn engages the swash-plate 32 which in turn is in engagement with the housing part 13. In this connection, there may be some movement of the collar 52 due to some distortion of the plate 57. However, this would be extremely minimal and for purposes of description will be ignored.

The movement of the fixture 70 causes the cylinder 20 to be pressfit to its final position relative to the collar 52, as shown in FIG. 4. At the same time, the spring member 62 is compressed by this movement of the fixture 70. The fixture 70 bottoms out or more specifically stops movement when the surface portion 75 thereof engages the gasket 69. The gasket 69, of course, being a compressible member may be compressed by movement of the fixture member 70 to some extent, and this may affect the clearance which is provided in the final assemblage. However, in essence, for purposes of understanding the present invention, it can be assumed that the gasket 69 is not compressed and that when the fixture surface 75 engages the gasket 69, further movement of the fixture 70 ceases, as shown in FIG. 4.

The fixture 70 is then removed from the assemblage and the bearing 14 is positioned around the shaft 111 and the end plate 15 is bolted onto the housing 16. It should be noted that the end plate 15 does not have a projecting portion which corresponds with the portion 71 of the fixture 70, but rather the end plate 15 has a generally flat interior surface which at its outer periphery engages the gasket 69 to provide a fluid seal therebetween. In view of this construction of the end plate 15, when it is assembled in position on the housing portion 16, the spring 62 urges the cylinder block toward the right, as viewed in the drawings, and urges the valve plate 42 into engagement with the inner surface of the cover member 15. As a result, the cylinder block 20 is disposed toward the right from its position shown in FIG. 4 to its position of FIG. 1 by the spring 62 and, in fact, the spring 62 biases or moves the cylinder block 20 from its position shown in FIG. 4 toward the right, carrying with it the spherical collar member 52 which is pressfit at 53 to the hub portion 51 of the cylinder block. This results in clearance being established between the parts interposed between the thrust plate 31 and the collar 52. While this clearance is shown at 60 in FIG. ll, it should be clear that the retainer plate 57 is floating in its position, when assembled and the clearance may occur at other locations. Moreover, the clearances and relative positions during assembly are exaggerated somewhat in the drawings for purposes of illustration, which should be readily apparent to those skilled in the art.

From the above, it should be clear that applicant has provided a new hydraulic fluid device having a prede: termined clearance and a method of assembly provid ing for such clearance which allows for axial relative movement between the thrust plate 31 and the slippers 23 and also between the slippers 23 and the slipper'retainer plate member 57, as well as between the slipper retainer 5'7 and collar 52.

What is claimed is:

l. A hydraulic fluid device including a cylinder block having ahub portion at one end thereof, a plurality of pistons with inner ends disposed for reciprocation within the cylinders in said cylinder block and protruding therefrom at said one end of said cylinder block, an inclined cam plate facing said one end of said cylinder block, a bearing surface on said cam plate, the other ends of said pistons having bearing means for slidably following said bearing surface, means mounting said cylinder block and cam plate for relative rotation, inlet and outlet means communicating successively with ports from said cylinders upon relative rotation of said cylinder block and said cam plate, a collar fixedly secured on said hub portion by a pressfit interconnection therebetween and being free of any bias toward said bearing surface, said collar having a spherical outer surface, a retainer plate for said bearing means supported on said spherical outer surface of the collar and having a portion cngageable with said bearing means, and spring means biasing said cylinder block and said collar in a direction away from said bearing means thereby establishing clearance between said retainer plate and said bearing means.

2. A hydraulic fluid device as defined in claim ll further including a housing for said cylinder block, and wherein a shaft extends into said housing, said hub portion of said cylinder block and said shaft having a drivetransmitting engagement, and said spring means acting between said shaft and said cylinder block.

3. A hydraulic fluid device as defined in claim 2 wherein said housing has an end cover portion, and a valve plate engageable with the end surface of said cylinder block and biased against said end cover by said spring means.

4. A method of assembling a hydraulic fluid device which includes a cylinder block having a hub portion at one end thereof, a plurality of pistons with inner ends disposed for reciprocation within cylinders in the cylinder block and protruding therefrom at the one end of the cylinder block, an inclined cam plate facing said one end of said cylinder block, a bearing surface on said cam plate, the outer ends of said pistons having bearing means for slidably following said bearing surface, said method of assembly including the steps of securing by pressfitting a spherical collar on the hub portion of the cylinder block to fix the spherical collar from movement relative thereto during operation of the hydraulic fluid device, supporting a retainer plate for the bearing means on the spherical outer surface of the collar and in engagement with the bearing means, and then biasing the cylinder block and the collar in a direction to establish a predetermined clearance between the retainer plate and the bearing means.

5. A method of assembling as defined in claim 1 wherein said hydraulic fluid device includes a housing and a drive shaft extending into the housing and further including the steps of assembling the rotary group, namely, the pistons, retainer plate, and cylinder block outside the housing, piloting the rotary group onto the drive shaft through an open end of the housing, and securing a cover plate-to close the open end of the housmg.

6. A method of assembling as defined in claim 5 wherein the spherical collar and hub portion of the cylinder block are partially pressfit together outside the housing and the pressfitting is completed after assembly in the housing by the step of applying a force to the cylinder block while restraining movement of the collar.

7. A method of assembling as defined in claim 6 wherein a spring acting between the drive shaft and cylinder block is compressed by the application of the force to the cylinder block to complete thee pressfitting thereof, and upon removal of the force the spring provides said biasing to establish said clearance.

5. A method of assembling a hydraulic fluid-device which includes a housing, a cylinder block having a hub portion at one end thereof in said housing, a drive shaft extending through the cylinder block and drivingly connectedtherewith, a plurality of pistons with inner ends disposed for reciprocation within cylinders in the cylinder block and protruding therefrom at the one end of the block, an inclined cam plate in said housing facing said one end of said cylinder block, a bearing surface on said cam plate, the outer ends of said pistons having bearing means for slidably following said bearing surface, said method of assembling including the steps of partially pressfitting a spherical collar on the hub portion of the cylinder block, inserting the cylinder block and spherical collar in their partially pressfit relationship into the housing and in telescoping relation with the drive shaft through an axial open end of the housing, supporting a retainer plate for the bearing means on the spherical outer surface of the collar and in engagement with the bearing means, placing a valve plate on the other end of the cylinder block, engaging the valve plate with a fixture and applying an axial force on the valve plate and cylinder block while resisting that force by engagement ef the collar with the retainer plate, retainer plate with the bearing means, and bearing means with the cam plate to thereby complete the pressfitting of the spherical collar on the hub portion of the cylinder block to fix it thereon, compressing a spring acting between the cylinder block and shaft by movement of the fixture, removing the fixture, assembling a housing closure plate on the open end of the housing, and enabling the spring to move the cylinder block and collar in a direction away from the bearing means to establish a predetermined clearance between the retainer plate and bearing means.

UNITED STATES PATENT OFFICE CERTIFICATE 01% CORRECTION Patent MBLM Dated January 8, 1m

Inventor(s) Roger J. Benkovic It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 3, line 59, "wtih" should read with Column 5, Claim 1, line 56, "other should read outer Column 6, claim 7, line 55, thee" should read the Signed and sealed this 30th day of April 197A.

(SEAL) Atte st: 7

EDI/JAM) DLFLETCIERJR. C. MARSHALL DAMN Atte sting; Officer I Commissioner of Patents EM FP' v uscomm-oc wan-Pea v u.s. eovgmmpq ymrjimc orncz: I919 c ass-3:4, 

1. A hydraulic fluid device including a cylinder block having a hub portion at one end thereof, a plurality of pistons with inner ends disposed for reciprocation within the cylinders in said cylinder block and protruding therefrom at said one end of said cylinder block, an inclined cam plate facing said one end of said cylinder block, a bearing surface on said cam plate, the other ends of said pistons having bearing means for slidably following said bearing surface, means mounting said cylinder block and cam plate for relative rotation, inlet and outlet means communicating successively with ports from said cylinders upon relative rotation of said cylinder block and said cam plate, a collar fixedly secured on said hub portion by a pressfit interconnection therebetween and being free of any bias toward said bearing surface, said collar having a spherical outer surface, a retainer plate for said bearing means supported on said spherical outer surface of the collar and having a portion engageable with said bearing means, and spring means biasing said cylinder block and said collar in a direction away from said bearing means thereby establishing clearance between said retainer plate and said bearing means.
 2. A hydraulic fluid device as defined in claim 1 further including a housing for said cylinder block, and wherein a shaft extends into said housing, said hub portion of said cylinder block and said shaft having a drive-transmitting engagement, and said spring means acting between said shaft and said cylinder block.
 3. A hydraulic fluid device as defined in claim 2 wherein said housing has an end cover portion, and a valve plate engageable with the end surface of said cylinder block and biased against said end cover by said spring means.
 4. A method of assembling a hydraulic fluid device which includes a cylinder block having a hub portion at one end thereof, a plurality of pistons with inner ends disposed for reciprocation within cylinders in the cylinder block and protruding therefrom at the one end of the cylinder block, an inclined cam plate facing said one end of said cylinder block, a bearing surface on said cam plate, the outer ends of said pistons having bearing means for slidably following said bearing surface, said method of assembly including the steps of securing by pressfitting a spherical collar on the hub portion of the cylinder block to fix the spherical collar from movement relative thereto during operation of the hydraulic fluid device, supporting a retainer plate for the bearing means on the spherical outer surface of the collar and in engagement with the bearing means, and then biasing the cylinder block and the collar in a direction to establish a predetermined clearance between the retainer plate and the bearing means.
 5. A method of assembling as defined in claim 4 wherein said hydraulic fluid device includes a housing and a drive shaft extending into the housing and further including the steps of assembling the rotary group, namely, the pistons, retainer plate, and cylinder block outside the housing, piloting the rotary group onto the drive shaft through an open end of the housing, and securing a cover plate to close the open end of the housing.
 6. A method of assembling as defined in claim 5 wherein the spherical collar and hub portion of the cylinder block are partially pressfit together outside the housing and the pressfitting is completed after assembly in the housing by the step of applying a force to the cylinder block while restraining movement of the collar.
 7. A method of assembling as defined in claim 6 wherein a spring acting between the drive shaft and cylinder block is compressed by the application of the force to the cylinder block to complete thee pressfitting thereof, and upon removal of the force the spring provides said biasing to establish said clearance.
 8. A method of assembling a hydraulic fluid device which includes a housing, a cylinder block having a hub portion at one end thereof in said housing, a drive shaft extending through the cylinder block and drivingly connected therewith, a plurality of pistons with inner ends disposed for reciprocation within cylinders in the cylinder block and protruding therefrom at the one end of the block, an inclined cam plate in said housing facing said one end of said cylinder block, a bearing surface on said cam plate, the outer ends of said pistons having bearing means for slidably following said bearing surface, said method of assembling including the steps of partially pressfitting a spherical collar on the hub portion of the cylinder block, inserting the cylinder block and spherical collar in their partially pressfit relationship into the housing and in telescoping relation with the drive shaft through an axial open end of the housing, supporting a retainer plate for the bearing means on the spherical outer surface of the collar and in engagement with the bearing means, placing a valve plate on the other end of the cylinder block, engaging the valve plate with a fixture and applying an axial force on the valve plate and cylinder block while resisting that force by engagement ef the collar with the retainer plate, retainer plate with the bearing means, And bearing means with the cam plate to thereby complete the pressfitting of the spherical collar on the hub portion of the cylinder block to fix it thereon, compressing a spring acting between the cylinder block and shaft by movement of the fixture, removing the fixture, assembling a housing closure plate on the open end of the housing, and enabling the spring to move the cylinder block and collar in a direction away from the bearing means to establish a predetermined clearance between the retainer plate and bearing means. 